Yes, obviously it is about the day/night cycle and not about absolute time because people on the other side of the planet are just fine. But while the absolute

Yes, obviously it is about the day/night cycle and not about absolute time because people on the other side of the planet are just fine. But while the absolute time may not matter, the time you are awake during the day/night cycle does matter. You can try to tell yourself you can live outside this day/night cycle, but we just didn't evolve that way.